From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B42C2C433E6 for ; Mon, 8 Feb 2021 17:48:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 69C1B64E88 for ; Mon, 8 Feb 2021 17:48:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235093AbhBHRsC (ORCPT ); Mon, 8 Feb 2021 12:48:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:36948 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233911AbhBHPbi (ORCPT ); Mon, 8 Feb 2021 10:31:38 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A290064F37; Mon, 8 Feb 2021 15:17:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1612797456; bh=oGYFLcwBYUzIxPOwoh/aKsUxQYKMGRHnAS+QCYCIaTs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L/tQYQzYHVso8zMUzuQXom7trBXU8UiL/DSrzalit8eOMO6dCRL388s6bRIddpSu5 9Pp3D+BMjA3xTChhDSOiQrYArBWf8gdKWxud9XuPI6pOaa7wHqolBBzY2p3f2z5ERE kphBws32Wo5oDHNHqV++8cnx6iYbZRtpTxzeIq/0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Chinmay Agarwal , Cong Wang , David Ahern , Jakub Kicinski Subject: [PATCH 5.10 116/120] neighbour: Prevent a dead entry from updating gc_list Date: Mon, 8 Feb 2021 16:01:43 +0100 Message-Id: <20210208145822.990723934@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210208145818.395353822@linuxfoundation.org> References: <20210208145818.395353822@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Chinmay Agarwal commit eb4e8fac00d1e01ada5e57c05d24739156086677 upstream. Following race condition was detected: - neigh_flush_dev() is under execution and calls neigh_mark_dead(n) marking the neighbour entry 'n' as dead. - Executing: __netif_receive_skb() -> __netif_receive_skb_core() -> arp_rcv() -> arp_process().arp_process() calls __neigh_lookup() which takes a reference on neighbour entry 'n'. - Moves further along neigh_flush_dev() and calls neigh_cleanup_and_release(n), but since reference count increased in t2, 'n' couldn't be destroyed. - Moves further along, arp_process() and calls neigh_update()-> __neigh_update() -> neigh_update_gc_list(), which adds the neighbour entry back in gc_list(neigh_mark_dead(), removed it earlier in t0 from gc_list) - arp_process() finally calls neigh_release(n), destroying the neighbour entry. This leads to 'n' still being part of gc_list, but the actual neighbour structure has been freed. The situation can be prevented from happening if we disallow a dead entry to have any possibility of updating gc_list. This is what the patch intends to achieve. Fixes: 9c29a2f55ec0 ("neighbor: Fix locking order for gc_list changes") Signed-off-by: Chinmay Agarwal Reviewed-by: Cong Wang Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20210127165453.GA20514@chinagar-linux.qualcomm.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/core/neighbour.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1245,13 +1245,14 @@ static int __neigh_update(struct neighbo old = neigh->nud_state; err = -EPERM; - if (!(flags & NEIGH_UPDATE_F_ADMIN) && - (old & (NUD_NOARP | NUD_PERMANENT))) - goto out; if (neigh->dead) { NL_SET_ERR_MSG(extack, "Neighbor entry is now dead"); + new = old; goto out; } + if (!(flags & NEIGH_UPDATE_F_ADMIN) && + (old & (NUD_NOARP | NUD_PERMANENT))) + goto out; ext_learn_change = neigh_update_ext_learned(neigh, flags, ¬ify);